1. Field of the Invention
The present invention relates to a knitted fabric presser of a flat knitting machine, particularly to such a presser which is installed at a carriage unit to be movable between a pressing position where the presser is operative and a resting position where the presser is inoperative.
2. Description of the Related Art
Conventionally, a knitted fabric presser as shown in FIG. 20 is used at each lock of a carriage unit in a flat knitting machine, especially, V-bed type flat knitting machine. The knitted fabric presser is also called a stitch presser. A horizontal portion of an L-shaped presser 101 presses a knitted fabric 102 from above. In a flat knitting machine of the V-bed type, a front needle bed 103 and a rear needle bed 104 are arranged opposite to each other in a reversed V arrangement. Press functioning of the presser 101 is conducted at a gap 105 formed between the front needle bed 103 and the rear needle bed 104. When knitting needles 106, 107 ascend for knitting or transferring, by pressing the knitted fabric 102 inside the gap 105, uppermost loops 108, 109 of the knitted fabric 102 are prevented from moving. When pressing is not necessary, the presser 101 is moved from the gap 105 without touching sinkers 110, 111.
The presser 101, which is generally L-shaped, presses the knitted fabric 102 by a horizontal portion thereof extending along a direction of movement of a carriage. A portion of the presser 101 transverse to the direction of movement of the carriage is attached to a mechanism which makes the presser 101 move in conjunction with the carriage. A yarn for knitting the fabric 102 is fed to points of the knitting needles 106, 107 almost in the middle of the horizontal portion of the presser 101. The vertical portion of the presser 101 must be placed upstream of a knitting direction in order to space the presser 101 from the loops 108, 109 formed by knitting action of the knitting needles 106, 107. Therefore, both forward and backward movements of presser 101 are necessary in order to reciprocally knit in relation to longitudinal directions of the needle beds 103,104. A sufficient length of the horizontal portion of the presser 101 is required in order to satisfactorily press the knitted fabric 102. Though it is possible to turn the direction of the horizontal portion on the assumption that the vertical portion is a rotation axis, that requires an impractically large space. It is a practical arrangement that pressers 101 for respective forward and backward movements are provided, and a particular presser 101 is actuated according to a particular movement direction.
There are generally two ways to install a stitch presser as shown in FIG. 20. One way is to install the stitch presser on an upper portion of a cam box of the carriage crossing over the front and rear needle beds. The other way is to install the stitch presser on a yarn guide rail provided just above a gap along a longitudinal direction of the needle bed.
A prior art arrangement of the type to install the presser on the upper portion of a cam box is disclosed, for example, in Japanese Examined Patent Publication JP(B2) 62-15662 and JP(B2) 3-66415. According to the arrangement disclosed in JP(B2) 62-15662, a presser for forward movement is installed on an upper portion of one cam box, and a presser for backward movement is installed on another cam box. At the upper parts of both pressers are provided pins which are engaged with grooved cams. When a grooved cam reaches a receiving piece fixed on a respective longitudinal end of the needle bed, the respective presser is switched to be operative or inoperative. Further, according to the prior art arrangement disclosed in JP(B2) 3-66415, function or non-function of the presser is switched by using a stepping motor and a swing arm.
A prior art arrangement with a stitch presser installed on a yarn guide rail is disclosed, for example, in Japanese Unexamined Patent Publication JPA 58-46156. According to such arrangement, the stitch presser, moving together with a carriage, is installed on the yarn guide rail just above a gap, and the direction of movement of the presser is changed by receiving pieces provided at opposite ends of a needle bed. Though a large number of yarn feeders are required to run in a flat knitting machine, employing such type of stitch presser installed on a yarn guide rail causes a decrease of the number of yarn feeders capable of running.
In the prior art arrangement disclosed in JP(B2) 62-15662 and JP(B2) 3-66415, the number of yarn feeders running on a yarn guide rail does not decrease because a stitch presser is installed on a carriage, which is different from the prior art arrangement disclosed in JP(B2) 58-46156. According to the arrangement disclosed in JP(B2) 62-15662 and JPA 58-46156, the direction of the presser cannot be changed unless a carriage reaches either of the longitudinal ends of the needle bed. In the arrangement disclosed in JP(B2) 3-66415, since function or non-function of a presser is switched by drive of a stepping motor, it is possible to conduct switching at any position regarding the longitudinal direction of the needle bed.
In certain cases of a flat knitting machine, it is unnecessary to use the entire longitudinal width of the needle bed for knitting. In such cases, if a presser does not need to be switched, it is possible to knit quickly by reciprocally moving a carriage only in a region where a knitted fabric is formed. If it is necessary to move the carriage to a longitudinal end of the needle bed in order to switch a presser, knitting time cannot be reduced no matter how narrow may be the width of the knitted fabric.
According to the arrangement disclosed in JP(B2) 3-66415, function or non-function of a presser can be switched at any longitudinal position of the needle bed by a unit including a stepping motor and a swing arm. That, however, requires a large size carriage or limits positions of installation because respective units are needed for forward and backward movements. On the other hand, according to the arrangement disclosed in JP(B2) 62-15662 and JP(B2) 3-66415, respective pressers for forward and backward movements should be arranged separately on carriages for front and rear needle beds. This is because the respective pressers interfere with each other if they are arranged on the same carriage. More specifically, it is easy to prevent the pressers from interfering with each other when one presser is placed in a pressing position and the other presser is placed in a rest position. However, when both pressers are in rest positions or when the positions thereof are on route to be mutually changed, there is a high likelihood that they will interfere with each other because of overlapping of movement traces or paths of movement thereof. In case the horizontal portion of the presser is decreased in length, the probability of interference can be reduced. However, a knitted fabric cannot be pressed satisfactorily by a presser with a horizontal portion of short length.